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摘要: 為解決二氧化鈦（TiO2）光生載流子壽命短的問題，以鈦酸四丁酯、氟化鈉和石墨粉為原料，采用水熱法制備了NaF–TiO2/rGO復合材料，通過透射電鏡（TEM）、X射線能譜分析（EDS）、X射線衍射（XRD）、光致發光光譜（PL）、紫外漫反射光譜（UV–Vis）對復合材料的微觀形貌、物相組成、晶型、熒光強度等特性進行了表征，并以降解羅丹明B（RhB）測試其光催化活性及降解機理。實驗結果表明，制備得到的產物主要為{001}、{101}晶面協同的銳鈦礦相TiO2并均勻分布于rGO表面，NaF與rGO的加入可有效降低其電子–空穴對的復合速率以及帶隙寬度從而提高光催化活性。在最佳制備條件下，催化反應80 min后對1×10–5 mol·L–1 羅丹明B（RhB）溶液的降解率可達99.8%，降解速率常數（0.0448 min–1）是NaF – TiO2的1.67倍，且復合材料的催化性能隨其投加量的增大先加強后保持穩定，pH適用范圍為3～11；自由基猝滅實驗結果表明，在光催化降解過程中，起主要作用的活性物質是·OH和h+。Abstract: TiO2 has been widely studied because of its excellent photocatalytic properties but still has defects, such as the short lifetime of the photogenerated carrier. To solve these problems, a novel NaF–TiO2/rGO composite has been successfully synthesized using the hydrothermal method. The photocatalyst complexes were characterized using transmission electron microscope (TEM), energy dispersive spectrometer (EDS), diffraction of X-rays (XRD), photoluminescence spectroscopy (PL), and ultraviolet–visible spectroscopy (UV–Vis). This paper investigates the effects of hydrothermal temperature, hydrothermal time, rGO content, and NaF content on the photocatalytic activity of the NaF–TiO2/rGO composite, and the photocatalytic activity is evaluated using the photocatalytic degradation of RhB under fluorescent lamp illumination for approximately 80 min. The TEM analysis and identification results indicate that rGO can be incorporated into TiO2 to form a heterogeneous structure. The XRD results show that no heterophase formation occurs in the prepared NaF – TiO2/rGO composite, and the NaF – TiO2/rGO composite on the rGO surface does not cause the crystal shape change of the anatase phase. The PL results indicate that the main products are TiO2 with {001} and {101} facet synergy, and adding rGO effectively reduces the electron–hole pair recombination rate. The UV–Vis results show that the band gap energy of TiO2 is reduced by introducing NaF and further reduced after rGO is combined, thereby enhancing the photocatalytic activity and efficiency of TiO2. Compare and analyze RhB degradation using different factor systems and determine the best synthesis process for preparing composite materials at a hydrothermal temperature of 100 ℃, a hydrothermal time of 10 h, an rGO content of 0.3%, and a NaF content of 30%. The composite material had the best photocatalytic activity. The photocatalytic test results indicate that NaF–TiO2/rGO synthesized using the hydrothermal method has a better light absorption efficiency. The samples have a better RhB degradation rate under simulated solar irradiation. The RhB degradation followed pseudo-first-order reaction kinetics with a rate constant of 0.0448 min?1, which is 1.67 times that of NaF–TiO2. The RhB degradation rate over 80 min reached 99.8%, increasing first and then remaining constant with increasing NaF–TiO2/rGO dosage. Additionally, NaF–TiO2/rGO has good catalytic activity in the pH range of 3?11. The results of free radical capture showed that all three kinds of free radicals participated in RhB photocatalytic degradation, and the main active species in the reaction system should be ·OH and h+.
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Key words:
- rGO /
- facets synergy of TiO2 /
- photocatalysis /
- RhB /
- degradation mechanism
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圖 1 TiO2（a）、NaF–TiO2（b）和NaF–TiO2/rGO（c~d）的TEM圖及NaF–TiO2/rGO的EDS(e)分析圖
Figure 1. TEM images of TiO2 (a), NaF–TiO2 (b), and NaF–TiO2/rGO (c and d) and EDS elemental mapping analysis of NaF–TiO2/rGO (e)
圖 2 TiO2、NaF–TiO2和NaF–TiO2/rGO的XRD圖
Figure 2. XRD patterns of TiO2, NaF–TiO2, and NaF–TiO2/rGO
圖 3 TiO2、NaF–TiO2和NaF–TiO2/rGO的PL圖
Figure 3. PL spectra of TiO2, NaF–TiO2, and NaF–TiO2/rGO
圖 4 TiO2、NaF–TiO2和NaF–TiO2/rGO的紫外–可見吸收光譜圖（a）以及帶隙圖（b）
Figure 4. UV–Vis spectra (a) and bandgap (b) images of TiO2, NaF–TiO2, and the NaF–TiO2/rGO heterojunction
圖 5 rGO的質量分數（a）、水熱溫度（b）、水熱時間（c）、NaF的質量分數（d）對光催化活性的影響
Figure 5. Effect of the amount of rGO added (a), the temperature (b), the time of the hydrothermal treatment (c), and the amount of NaF added (d) to the reaction solution on photocatalytic reduction
圖 6 反應pH對光催化活性的影響
Figure 6. Effect of the pH of the reaction solution on photocatalytic reduction
圖 7 復合材料濃度對光催化活性的影響
Figure 7. Effect of the composite concentration of the reaction solution on photocatalytic reduction
圖 8 RhB濃度對光催化活性的影響
Figure 8. Effect of the RhB concentration of the reaction solution on photocatalytic reduction
圖 9 NaF–TiO2/rGO復合材料對RhB的降解機理圖
Figure 9. Degradation mechanism diagram of RhB by composite materials
表 1 不同捕獲劑對RhB光降解的影響
Table 1. Effects of different trapping agents on RhB photodegradation
Radical scavenger First-order kinetics equations k/min?1 t(1/2)/min Contribute/% Blank ln(c0/ct)=0.0448t+0.3597，R2=0.927 0.0448 7.4 — IPA ln(c0/ct)=0.0027t+0.005，R2=0.965 0.0027 253.7 93.9 BQ ln(c0/ct)=0.0203t–0.034，R2=0.997 0.0203 35.7 54.7 EDTA-2Na ln(c0/ct)=0.0046t+0.006，R2=0.995 0.0046 148.7 89.7 
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